HIV immune reconstitution inflammatory syndrome (IRIS) is a newly recognized complication of anti- retroviral therapy (ART) whereby a portion of patients with advanced HIV who initiate ART subsequently experience paradoxical clinical worsening due to exaggerated inflammatory responses to occult, latent, or previously treated infections. HIV IRIS has emerged as a frequent complication of ART in sub-Saharan Africa. Our long term goal is to understand the pathogenesis of IRIS so we can develop optimized ART regimens to minimize the morbidity and mortality associated with IRIS in resource limited regions. We are currently performing a study in HIV-infected patients in Uganda as they initiate ART to better understand the impact of IRIS in Sub-Saharan Africa. The goals of the ongoing study are to evaluate the incidence, severity and clinical features of IRIS and to determine if HIV-infected Ugandan patients who develop IRIS have worse clinical outcomes compared to patients who do not develop IRIS. We are prospectively following 100 HIV-infected Ugandan patients for one year after they initiate ART. Of these, 50 patients have no active OI at time of ART initiation, and 50 patients have a diagnosis of cryptococcal meningitis within the previous 2 months. In addition to determining the incidence, severity, and clinical features of IRIS after initiation of ART in these patients, we will also determine whether the development of an IRIS event has a negative effect on ART compliance and whether this impacts treatment success. For this R03 grant application, we plan to use blood specimens obtained from patients in our ongoing cohort study to evaluate immune activation. The specific aim is to identify predictive and diagnostic biomarkers of IRIS by comparing immune activation in the peripheral blood of patients who develop IRIS versus those who do not develop IRIS after initiation of ART. We will prospectively collect whole blood RNA before and after initiation of ART and will use Affymetrix microarrays to compare immune activation gene expression between patients who develop IRIS and patients who do not develop IRIS. In this way, we will identify specific biomarkers associated with IRIS that are diagnostic of IRIS or predictive of future IRIS. A goal is to identify biomarkers that can be adapted into simple, inexpensive assays, such as real time PCR or ELISA, that can be used clinically to diagnose IRIS or monitor patients at risk for IRIS. The identification of biomarkers of IRIS will also provide important insight into the immune activation pathways that underlie the pathophysiology of IRIS. PUBLIC HEALTH RELEVANCE: HIV immune reconstitution inflammatory syndrome (IRIS) has emerged in sub-Saharan Africa as an important complication to antiretroviral therapy to treat HIV infection. Patients who develop IRIS exhibit clinical worsening due to inflammatory reactions that occur as their immune systems improve after starting antiretroviral therapy. The goal of this study is to develop clinical blood tests that could be used to diagnose IRIS and predict patients who are at risk for its development before they become ill.